<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>
		<a href="#" title="你好" class="red" id="app">黑马程序员</a>
	</body>
	<!--
		下面两种写法是等价的
		<script></script>
		<script type="text/javascript"></script>
	-->
	<!--<script></script>-->
	<script type="text/javascript">
		var oApp =  document.getElementById("app")
		// 修改标签里面class的属性
		oApp.className = 'blue'
		// 获取到标签里面的值
		
	</script>

</html>